• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.6
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• pp.752-759
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• 2014

Varieties of research on turbulent-induced noise is conducted with combinations of acoustic analogy methods and computational fluid dynamic methods to analyze efficiently and accurately. Application of FW-H acoustic analogy without turbulent noise is the most popular method due to its calculation cost. In this paper, turbulent-induced noise is predicted using RANS turbulence model and permeable FW-H method. For simplicity, noise from 2D cylinder is examined using three different methods, direct method of RANS, FW-H method without turbulent noise and permeable FW-H method which can take into account of turbulent-induced noise. Turbulent noise was well predicted using permeable FW-H method with same computational cost of original FW-H method. Also, ability of permeable FW-H method to predict highly accurate turbulent-induced noise by applying adequate permeable surface is presented. The procedure to predict turbulent-induced noise using permeable FW-H is established and its usability is shown.

• Journal of Soil and Groundwater Environment
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• v.13 no.3
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• pp.37-44
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• 2008

Soil ecology has important roles in global ecosystems. However, soil ecological quality information is being ignored when assessing ecological impact of construction actions. And methods for classifying and assessing soil ecological quality have been very little established in comparison to those for animal and plant ecosystems. In this study, it was examined whether soil ecological quality information has influence on determining an eco-friendly route for a road construction project. For this, sensitivity analysis was systematically performed by varying the relative significance (weights) of soil ecological quality information among natural environmental and ecological factors. When the weight of soil ecological quality was greater than just 14%, the soil ecological quality information significantly influenced the determination of the eco-friendly routes for a specific road construction project. This demonstrates that soil ecological quality information has to be considered for more reliable environmental impact assessment, and also supports the validity of use of soil ecological quality information and its mapping technique in planning and siting of eco-friendly construction projects.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.66 no.3
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• pp.265-269
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• 2021

This study was conducted to provide primary data through analysis of zoysia grass genetic resources to develop grass cultivars with beneficial novel properties. Zoysia grass (Zoysia. spp) is native to Korea, and is mainly propagated through stolons. However, since seed coat treatment technology was developed, the breeding of sexually reproductive grass variants has become possible, necessitating characterization of the floret appearance rate in the secured zoysia grass genetic resource before developing sexually reproductive cultivars. In this experiment, 549 grass lines were examined, revealing that florets appear in only 43 lines (7.81%). Survival rates after transplantation, and stolon generation rates displayed a significant positive correlation (Rho = 0.44). Survival rates after transfer, and rates of stolon production displayed very low correlations with floret appearance (Rho = -0.11 and Rho = -0.06). No significant results were obtained in 43 lines that displayed >20% floret appearance. To breed sexually reproductive grass variants, it is thus necessary to secure more genetic resources, considering the low rate of floret appearance. Finding traits that predict floret appearance at an early stage is also required.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.39 no.4
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• pp.235-243
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• 2021

River surveying is conducted to acquire basic geographic data for river master plans and various river maintenance, and it is also used to predict changes after river maintenance construction. ABL (Airborne Bathymetric LiDAR) system is a cutting-edge surveying technology that can simultaneously observe the water surface and river bed using a green laser, and has many advantages in river surveying. In order to use the ABL data for river surveying, it is prerequisite step to segment and extract the water surface and river bed points from the original point cloud data. In this study, point cloud segmentation was performed by applying the ground filtering technique, ATIN (Adaptive Triangular Irregular Network) to the ABL data and then, the water surface and riverbed point clouds were extracted sequentially. In the Gokgyocheon river area, Chungcheongnam-do, the experiment was conducted with the dataset obtained using the Leica Chiroptera 4X sensor. As a result of the study, the overall classification accuracy for the water surface and riverbed was 88.8%, and the Kappa coefficient was 0.825, confirming that the ABL data can be effectively used for river surveying.

• Korean Journal of Remote Sensing
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• v.37 no.5_3
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• pp.1405-1423
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• 2021

Precipitation is one of the main factors that affect water and energy cycles, and its estimation plays a very important role in securing water resources and timely responding to water disasters. Satellite-based quantitative precipitation estimation (QPE) has the advantage of covering large areas at high spatiotemporal resolution. In this study, machine learning-based rainfall intensity models were developed using Himawari-8 Advanced Himawari Imager (AHI) water vapor channel (6.7 ㎛), infrared channel (10.8 ㎛), and weather radar Column Max (CMAX) composite data based on random forest (RF). The target variables were weather radar reflectivity (dBZ) and rainfall intensity (mm/hr) converted by the Z-R relationship. The results showed that the model which learned CMAX reflectivity produced the Critical Success Index (CSI) of 0.34 and the Mean-Absolute-Error (MAE) of 4.82 mm/hr. When compared to the GeoKompsat-2 and Precipitation Estimation from Remotely Sensed Information Using Artificial Neural Networks (PERSIANN)-Cloud Classification System (CCS) rainfall intensity products, the accuracies improved by 21.73% and 10.81% for CSI, and 31.33% and 23.49% for MAE, respectively. The spatial distribution of the estimated rainfall intensity was much more similar to the radar data than the existing products.

• Korean Journal of Construction Engineering and Management
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• v.22 no.5
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• pp.86-98
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• 2021

In this study, we developed a simulation model for supply chain management of Precast Concrete (PC) based construction. To this end, information on the Factory Production/Site Construction system was collected through literature review and field research, and based on this information, a simulation model was defined by describing the supply chain, entities, resources, and processes. Next, using the Arena simulation software, a simulation model for the PC supply chain was developed by setting model frameworks, data modules, flowchart modules, and animation modules. Finally, verification and validation were performed using five review methodologies such as model check, animation check, extreme value test, average value test, and actual case test to the developed model. As a result, it was found that the model adequately represented the flows and characteristics of the PC supply chain without any logical errors and provided accurate performance evaluation values for the target supply chains. It is expected that the proposed simulation model will faithfully play a role as a performance evaluation platform in the future for developing management techniques in order to optimally operate the PC supply chain.

• Journal of Korea Water Resources Association
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• v.54 no.5
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• pp.347-354
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• 2021

In the past few years, various damages have occurred in the vicinity of rivers due to flooding. In order to alleviate such flood damage, structural and non-structural measures are being established, and one of the important non-structural measures is to establish a flood warning system. In general, in order to establish a flood warning system, the water level of the flood alarm reference point is set, the critical flow corresponding thereto is calculated, and the warning precipitation amount corresponding to the critical flow is calculated through the Geomorphological Instantaneous Unit Hydrograph (GIUH) rainfall-runoff model. In particular, when calculating the critical flow, various studies have calculated the critical flow through the Manning formula. To compare the adequacy of this, in this study, the critical flow was calculated through the HEC-RAS model and compared with the value obtained from Manning's equation. As a result of the comparison, it was confirmed that the critical flow calculated by the Manning equation adopted excessive alarm precipitation values and lead a very high flow compared to the existing design precipitation. In contrast, the critical flow of HEC-RAS presented an appropriate alarm precipitation value and was found to be appropriate to the annual average alarm standard. From the results of this study, it seems more appropriate to calculate the critical flow through HEC-RAS, rather than through the existing Manning equation, in a situation where various river projects have been conducted resulting that most of the rivers have been surveyed.

• Journal of Soil and Groundwater Environment
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• v.26 no.6
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• pp.106-117
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• 2021

The purpose of this study is prediction of landslide occurrence reflecting the subsurface flow characteristics within the soil layer in the future due to climate change in a large scale watershed. To do this, we considered the infinite slope stability theory to evaluate the landslide occurrence with predicted soil moisture content by SWAT model based on monitored data (rainfall-soil moisture-discharge). The correlation between the SWAT model and the monitoring data was performed using the coefficient of determination (R²) and the model's efficiency index (Nash and Sutcliffe model efficiency; NSE) and, an accuracy analysis of landslide prediction was performed using auROC (area under Receiver Operating Curve) analysis. In results comparing with the calculated discharge-soil moisture content by SWAT model vs. actual observation data, R² was 0.9 and NSE was 0.91 in discharge and, R² was 0.7 and NSE was 0.79 in soil moisture, respectively. As a result of performing infinite slope stability analysis in the area where landslides occurred in the past based on simulated data (SWAT analysis result of 0.7~0.8), AuROC showed 0.98, indicating that the suggested prediction method was resonable. Based on this, as a result of predicting the characteristics of landslide occurrence by 2050 using climate change scenario (RCP 8.5) data, it was calculated that four landslides could occur with a soil moisture content of more than 75% and rainfall over 250 mm/day during simulation. Although this study needs to be evaluated in various regions because of a case study, it was possible to determine the possibility of prediction through modeling of subsurface flow mechanism, one of the most important attributes in landslide occurrence.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.601-610
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• 2021

The tidal current patterns at Keum River Estuary before and after the construction of coastal structures were compared according to the CASES. The depth-integrated and tidal difference treatment applied FLOW2DH numerical model was used for the tidal current predictions. The test conditions consisted of before construction of coastal structures (CASE1), after construction of coastal structures (CASE2), and the addition of watergate operation(CASE1Q and CASE2Q), and present (CASE3). CASE1 showed a stable tidal current pattern, such as a natural estuary. In CASE2, the tidal current velocities and directions of the Keum River Estuary were changed due to the installed coastal structures. In particular, the tidal current velocities of the Gaeya open channel sections (P5~P9) in CASE2 were calculated to be 10~30% larger than that of CASE1. In the case of the Gunsan Inner Harbor (P4), which is closest to the Geum River Estuary, the ebb flow rate was approximately 250~300% faster than that of other CASEs due to the discharge of the watergate operation for 2.7 hours during the ebb of CASE1Q and CASE2Q. This will affect sediment transport, and it is predicted to lead to seabed changes. CASE3 is considered to be entering the stabilization stage according to the simulation of the tidal current velocities and directions of the Keum River Estuary and the surrounding coastal area.

• Korean Journal of Mineralogy and Petrology
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• v.34 no.2
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• pp.121-131
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• 2021

Magnesium (Mg) present in carbonate minerals as impurities has been used as a geochemical proxy to infer the environmental conditions where the minerals precipitated. The reliability of Mg geochemical proxies requires fundamental understanding of Mg incorporation into minerals based on accurate speciation of Mg ²⁺ in the crystal structure, which is determined mainly by application of X-ray absorption spectroscopy (XAS). However, high uncertainties are involved in interpreting the XAS spectra of minerals containing trace amount of Mg ²⁺. Because density function theory (DFT) can predict an XAS spectrum for a crystal structure, DFT calculations can reduce the uncertainties in the interpretation of the XAS spectrum. In this study, we calculated ab initio Mg K-edge absorption spectra of Mg silicates and (hydr)oxides based on DFT and analyzed the correlation between the calculated spectra and Mg structural parameters. Our ab initio Mg K-edge absorption spectra well reproduced the key features of the experimental spectra. The absorption-edge positions of the calculated spectra showed the weak positive correlation with the average Mg-O bond distance or Mg effective coordination number. The current study shows that DFT-based core-level spectroscopy method is a powerful tool in providing standard Mg K-edge spectra of diverse Mg minerals and determining the Mg chemical species within carbonate minerals.